How do northern grapes spend the winter?
Overwintering management of northern grapes is directly related to next year's yield and plant health. As a temperate vine, grape roots will be frostbitten at-5℃, and branches and buds will face the risk of death at-18℃. Based on the characteristics of severe cold winter in northern China, this paper systematically analyzes the key technologies and operating points for grape overwintering. Three-layer technical system for burying soil cold protection, freezing water Scientific irrigation and freezing water must be completed 15 days before soil freezing, and the water consumption per mu is controlled at 50-60 cubic meters. Clayey soil needs to be watered 20 days in advance, and sandy soil can be delayed to 10 days before freezing. The watering standard is to continue to penetrate for 2 hours after runoff is formed on the surface to ensure that a stable ice crystal protective layer is formed around the roots. When the average daily temperature of the key node buried for the first time stabilizes at 2℃ for three consecutive days, branch bundling and primary soil covering need to be completed. Use the "inverted U-shaped" binding method to ensure that the height of branches and vines from the ground does not exceed 30cm. The thickness of the covering soil is 8-12cm, and care should be taken to leave 5cm of branch tips exposed as ventilation holes. Secondary soil covering temperature control When the weather forecast shows that the lowest temperature is ≤-5℃ for 5 consecutive days, secondary soil covering shall be carried out. The thickness of the soil layer is increased to 60-80cm, and the width of the base is expanded to 2-2.5 meters, forming a trapezoidal cold-proof ridge. Add 3kg of crushed straw to each plant as an insulation layer, and combine with plastic film mulching to improve the insulation effect at 3-5℃. Water dynamic monitoring of the three core elements of wintering management establishes soil moisture monitoring points to maintain soil water content at 18-22%. A TDR probe is used to measure the moisture in the root layer every 7 days to prevent physiological freezing damage caused by winter drought. Temperature gradient control The buried soil area should maintain a temperature gradient of 0℃ to-5℃ and use NTC thermistors to monitor it in real time. When the rhizosphere temperature is ≤-8℃, cover needs to be replenished urgently. Pay special attention to temperature changes within 1.5 meters away from the main trunk. The incidence of freezing damage in this area accounts for 78% of the overall freezing damage. The three-dimensional protection of root systems adopts the "three principles of no excavation": do not dig soil within 50cm in radius of the rhizosphere, do not take mature soil from the cultivation layer, and do not use soil containing ice ballast. The soil cover should be taken from raw soil 2 meters away from the plant and used with a 0.04mm thick PE cold-proof film to reduce the depth of frozen soil by 23%.
Through a scientific buried soil cold-proof system and precise environmental control, the survival rate of northern grapes over winter can reach more than 95%. It is recommended to complete all cold-proof operations from mid-November to early December based on local climate characteristics, and regularly check the integrity of the covering soil. After spring, the cold-proof soil needs to be removed in three times and sprayed with antifreeze to achieve a safe transition.